The usual simplified view of Rydberg states of molecules as consisting of a single Rydberg electron loosely bound to a molecular ion core in a well-defined rotation-vibration state suggests an attractive possibility for state-selective production of molecular ions. A Rydberg electron excited above the energy of the ground state of the ion core will spontaneously autoionize, leaving behind a molecular ion. The autoionizing states are of strongly mixed character due to the ubiquitous nonadiabatic interactions between Rydberg series associated with different states of the ion core. Using our complete Multichannel Quantum Defect Theory (MQDT) fit model for CaF, we have predicted the locations and strengths of special autoionizing resonances that decay into a single rotation-vibration state of a molecular ion. Few molecules are as well characterized as CaF, nor as elegantly simple. We additionally describe the use of core nonpenetrating states as a general method to produce an ensemble of molecular ions in a single, selectable quantum state.
"Core nonpenetrating Rydberg states of molecules are a neglected state of matter. They could have a variety of uses, notably state-selective production of molecular ions. Due to the \textit{l}(\textit{l}+1)/r
2 centrifugal barrier that prevents the Rydberg electron in high-\textit{l} states from penetrating inside of the ion core, the electron is essentially uncoupled from the ion core, and the system becomes atom-like with long lifetimes, an ""almost good"" \textit{l} quantum number, and electronic transitions that follow
ΔJ
+=0 and
Δv
+=0 propensity rules. However, in most molecules access to these states, via a sequence of
Δ\textit{l}=+1 transitions from low-n*, low-\textit{l} states, is blocked by the necessity to traverse the ""zone of death,"" in which nonradiative decay mechanisms are prohibitively fast. We exploit Chirped Pulse millimeter-Wave (CPmmW) spectroscopy to efficiently excite Ca atoms and BaF molecules to core nonpenetrating states in the absence of nonradiative decay mechanisms. A universal method for preparing core nonpenetrating Rydberg states of molecules, which combines CPmmW spectroscopy with STImulated Raman Adiabatic Passage (STIRAP), will be discussed."
Aims: The Morgan’s Lab, at Wesleyan University – Connecticut, experimentally probed the dynamics of an atom/molecule using Semi-Classical approach. The experimental setup at Morgan’s Lab is designed to generate a neutral atomic or molecular beam, which is then excited with a finely tuned laser to Rydberg states; the highest quantized energy states the electron can be in before ionization. Study Design: In this current study, the potential of the Penning Ionization Gauge (PIG) as an ion source was evaluated for the Hydrogen atom. Place and Duration of Study: Physics Department, Wesleyan University, Middletown, Connecticut, USA, between June 2007 and August 2009. Methodology: The experimental setup is designed to generate a neutral atomic or molecular beam, which is then excited with a finely tuned laser to Rydberg states; the highest quantized energy states the electron can be in before ionization. The setup consists of an ion beam system consisting of a fast- metastable machine, vacuum pumping systems, an oven, a laser system consisting of a master YAG laser and a slave tunable dye laser, a second harmonic generator for doubling the frequency of the laser beam, Stark plate assembly, an ion detection system and a computer based data acquisition system with LABVIEW software. Results: The PIG found to populate the Hydrogen Rydberg states at 300% times more than the conventional ion source (8 µ Amp Vs. 2 µ Amp). Such high populations of ions lead to a high population of Rydberg states which in turn aided the overall experiment. Conclusion: A better understanding of the dynamics of an electron can aid experiments in condensed matter physics and molecular physics. Obtaining high population of Rydberg states can aid in increasing electron dynamic experiments by increasing the resolution of the scaled-energy absorption spectra. Penning Ionization Gauge (PIG) showed to have a better potential in producing high energy Rydberg states for the hydrogen gas.